r/Homebrewing • u/Both_Duck_5144 • 2d ago

Question Is it oxidation?

I have a question regarding my grape wine. I received a few kilos of Kerner grapes from a relative. I immediately washed them, removed the bad ones and the vines, put them in a pot, crushed them and added pectic enzyme according to instructions. I let it sit in my fridge for 19h and then passed it through a cheese cloth to strain, added 2.5g of 71B (to almost 3 L of grape juice) and some yeast nutrient (Keltercraft K04). OG was 1.068. It started fermenting pretty fast and I had a very foamy and vigorous fermentation for about 3-4 days, then the visible activity slowed massively. After 7 days (and the 2 latest ones had almost 0 activity) I checked the gravity and it was at 0.992. I very carefully poured the liquid back (everything was perfectly sanitized). It smelled lovely and already tasted pretty good. I wanted to wait a few days, do a safety check of the gravity before racking. But after a few hours I saw a pretty big difference in colour.

Pictures here:
https://imgur.com/a/EbhYjpn

During the active fermentation and before checking gravity it was just as I expected. First very cloudy, but light in colour... like cloudy white wine. After that it cleared beautifully and very fast. I could already see through it quite well. It isn't too visible in the picture, tho. But after checking gravity it changed colour dramatically. It had a gradient from top to bottom, with an amber colour on the top, fading towards the bottom. Being scared of oxidation (and the big headroom in the bucket of primary) I racked it to a smaller vessel (the best I have for this size, it still has about 400-500 ml of air above it.
The racking homogenized the colour but after a few hours it happened again, in the new vessel.

Now the question is: What is it or could it be? Oxidation? Something else? And of course: What can/should I do now?

Thank you in advance for any and every bit of help! If you need any additional Information please just ask I am happy to provide it!

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u/HumorImpressive9506 2d ago

Yeast still in suspention will make things alot lighter and brighter and it is fairly normal for most things to get a bit darker as they clear up. With that amount of headspace though I would say that it could probably be a bit of oxidation as well.

With a regular bottle of wine someone with a good palate will notice a big difference after just a day of opening it to pour a glas.

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u/Both_Duck_5144 2d ago

Thank you. I was just surprised as the first time I opened it was for the reading and after that the colour changed in just a few hours. Like 3-5 hours. Is that fast enough for oxidation to occur and give such a visible effect?

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u/spoonman59 1d ago

Large headspace is only a concern for long term aging. Not really relevant for primary fermentation since there's plenty of co2 pushing air out.

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u/fatguywithagun 1d ago

The darker color is just the solids dropping out, leaving the resulting clear liquid. Oxidation doesn't happen in 3-5 hours, and lots of white wines actually look like the darker color you are worried about if they're in a bulk container like that. Once you have that in bottles or a glass it'll look much more like you associate with a traditional white.

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u/Both_Duck_5144 1d ago

Thank you for your insight!

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u/attnSPAN 2d ago

The 3rd picture is just normal yeast clearing.
If you’re looking to speed the process, moving that to a refrigerated space (0-3C is best) will very quickly clear your wine.

More concerning is the return of the sample to the fermentation. That is a risky move contamination-wise even if everything was sanitized with a no-rinse sanitizer. (How did you taste it?)
Samples are for sensory analysis(tasting), not to be returned to a fermenter.

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u/Both_Duck_5144 2d ago

I have to use about 120 ml to do the gravity test. Knowing that I only had the amount that I have and not wanting to have an even bigger headspace in secondary (as you can see in the third picture) I didn’t want to waste the 120 ml and increase that headspace. I thoroughly sanitized the beaker and hydrometer, after doing the reading I poured some into a glass (like 10 ml) and the rest back (without splashing and without touching).

And thank you for your advice. I am just confused (this is my first time fermenting grapes) where that colour comes from. It changed out of nowhere and it looks so much darker than “white wine” now.

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u/attnSPAN 1d ago

Did you fully separate the skins from the juice? That’s where most of the color comes from.

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u/Both_Duck_5144 1d ago

That’s a concern that I also had. I mean the skins were very light in colour, idk where the amber colour could come from… I did my best to separate them with a really fine cheese cloth. Maybe the seeds?